This is the VOA Special English Health Report.

In December, we told you about two important studies of circumcision and HIV, the virus that causes AIDS. Scientists had reported that circumcised men in Africa reduced their risk of HIV infection from sex with women by about half.

Now, researchers are saying the reduction in risk may be greater than that.

The studies took place in Kenya and Uganda. The National Institutes of Health in the United States halted the work early. Officials said the results were so clear, it would have been wrong not to offer circumcision to all the men in the study groups.

Last week, the British medical magazine The Lancet published the final results of the two studies. The report also included findings from another study that took place earlier in South Africa. The researchers say the new results showed that circumcision could lower a man's HIV risk by as much as sixty percent.

Circumcision is the removal of the foreskin from the penis. Researchers have noted that HIV rates are generally lower in areas of the world where circumcision is common in babies or young boys. This fact alone does not prove anything. The studies were an attempt to confirm a direct link between circumcision and a reduced risk of HIV.

But how might circumcision reduce the risk? The experts at the National Institutes of Health say no one knows for sure, but there are several theories.

First, defensive cells on the surface of the foreskin may be less able to resist an attack by HIV than other cells. Also, the foreskin may serve as a barrier that prevents expulsion of HIV. And the environment of the foreskin may provide good conditions for the virus to spread.

Health experts involved in the studies say they hope circumcision will become one of the basic ways to fight AIDS. But they say it may be difficult to get men to have it done, especially if circumcision conflicts with their cultural beliefs. Other issues are cost and the availability of high-quality medical care. Since HIV can be passed through blood, unclean medical conditions might spread the virus.

Health experts also warn that while circumcision may reduce the risk of HIV, it does not offer complete protection.

And that's the VOA Special English Health Report, written by Caty Weaver. Our reports are online at voaspecialenglish.com and our e-mail address is special@voanews.com. Please be sure to include your name and country. I'm Mario Ritter.